From Jonathan McAlmont:
Fruitless Recursion is an online journal devoted to the review and discussion of works of criticism and non-fiction relating to the SF, Fantasy and Horror genres.
It is a paying market and it is currently looking for writers as well as subject matter. Go and have a look, I have kicked things off with a review of Paul Kincaid’s What it is We Do When We Read Science Fiction and Joanna Russ’ The Country You Have Never Seen.
Best of luck, Jonathan!